Field of the Invention
This invention generally relates to electrical food grinders, such as a coffee bean grinder, and more particularly, to means and methods for controlling the grinding operation of such a grinder.
Discussion of the Prior Art
Electrically powered commercial food grinders are well known in the art as shown by the coffee grinders shown in U.S. Pat. Nos. 6,499,628; 6,595,445; 6,626,085 and 7,264,186, all of which are hereby incorporated by reference. Briefly, such grinders generally comprise a hopper for containing the unground coffee beans, a grind chamber with rotatable grinding burrs, an auger, or screw conveyor for moving coffee beans from the hopper to the grinding chamber, an electrical motor mechanically linked to the grinding burrs to rotate them at high speed to grind the coffee beans within the grinding chamber. The ground coffee beans are automatically dispelled from the grinding chamber and into a suitable container such as a bag or re-sealable can. The control of the motor has in the past been controlled by means of a temporary contact push button electrical grind switch that is manually held in an actuated state to apply electrical power to the motor. The grinding burrs are driven to rotate only so long as the grind switch is held in an actuate state. Alternatively, the period of grinding is determined by means of a switch that is controlled by an electrical timer that applies power to the electrical motor for a preselected time period after initial actuation of a momentary contact grind switch. Different grind switches or positions may be associated with different associated preselected time period, electrical power is automatically removed and grinding stops regardless of whether all the coffee beans within the grinding chamber has been ground and dispensed out of the grinding chamber and into a suitable container, such as a bag.
Coffee grinders are often found in retail food stores that sell whole bean coffee and made available to customers to grind their coffee bean purchase in the store. In such a setting, the customer typically collects a desired amount of coffee beans to be ground in a bag or other container, deposits a the collected beans into the hopper, places the container beneath the outlet of the grinder and actuates the grind push-button switch. The grind switch is maintained in an actuated state until the customer decides that all the coffee beans have been ground or the grinding continues until a preselected time period selected by the customer has elapsed.
A problem arises when not all the coffee beans and residual ground coffee are not fully removed or completely exited from the grinding chamber either because the duration of the grinding time period that is selected is too short to insure that all the coffee and residue is removed or the customer fails to hold the grind actuation switch for a sufficiently long time to insure that the grinding chamber is fully cleared of all residual coffee. Complete removal generally requires the grinding to continue for several seconds after all the bulk coffee has been removed to also remove the fines and other residue that may still be present within the chamber and adhered to the burrs and other interior surfaces of the grinding chamber. Consequently, cross-contamination of different types and flavors of coffee occurs whenever the grinder is not operated a sufficiently long time to either dispel all the coffee fines and other residue after the bulk coffee has been dispelled, or worse, to dispel all the bulk coffee. For instance, vanilla flavored coffee could be mixed with hazelnut flavored coffee or a strong French roast might be mixed with a mild decaffeinated coffee. The cross contamination can be compounded across several successive incomplete grinding cycles resulting in an undesirable mixing of several different types and flavors.
Because of this cross-contamination, in known grinders it often becomes necessary to empty the entire grinder mechanism including the burrs and auger for cleaning between grinding cycles in which different types of coffee or other ingredient is being prepared.